Messages in this thread | | | Date | Mon, 8 Jun 2009 10:14:39 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v3] printk: add halt_delay parameter for printk delay in halt phase |
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* Dave Young <hidave.darkstar@gmail.com> wrote:
> Add a halt_delay module parameter in printk.c used to read the > printk messages in halt/poweroff/restart phase, delay each printk > messages by halt_delay milliseconds. It is useful for debugging if > there's no other way to dump kernel messages that time. > > The halt_delay max value is 65535, default value is 0, change it > by: > > echo xxx > /sys/module/printk/parameters/halt_delay > > Signed-off-by: Dave Young <hidave.darkstar@gmail.com> > --- > Documentation/kernel-parameters.txt | 5 +++++ > kernel/printk.c | 17 +++++++++++++++++ > 2 files changed, 22 insertions(+) > > --- linux-2.6.orig/kernel/printk.c 2009-06-08 13:55:35.000000000 +0800 > +++ linux-2.6/kernel/printk.c 2009-06-08 13:56:23.000000000 +0800 > @@ -250,6 +250,22 @@ static inline void boot_delay_msec(void) > } > #endif > > +/* msecs delay after each halt/poweroff/restart phase printk, > + unsigned short is enough for delay in milliseconds */ > +static unsigned short halt_delay; > + > +static inline void halt_delay_msec(void) > +{ > + if (unlikely(halt_delay == 0 || !(system_state == SYSTEM_HALT > + || system_state == SYSTEM_POWER_OFF > + || system_state == SYSTEM_RESTART))) > + return;
This is a tiny bit ugly (and goes into the vprintf path) but i can see no other way either - a system_state > SYSTEM_RUNNING check would needlessly include the suspend-to-disk state (which we dont want to include here).
In theory we could turn system_state into a bitmask and have a print_delay_mask check instead of these flags ... but that is a far wider change and i'm not sure it's a net step forwards.
I've applied your patch to tip:core/printk with small edits to the changelog - Linus & Andrew is Cc:ed, should they have any objections.
Ingo
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